Why are sliding window protocols required? What is the fundamental difference be

ID: 3682740 • Letter: W

Question

Why are sliding window protocols required? What is the fundamental difference between the GO Back to N and Selective Repeat protocols?

Q. 3. (a) Why are the sliding window protocols required? What is the fundamental difference between the GO Back to N and Selective Repeat protocols? In an example TCP com (numbered 0 through 9) are to be sent to a peer TCP layer. Assuming a window a size of 5,, illustrate with two separate message flow diagrams between theR sender-side and receiver-side TCP layers how the GO Back to N and Selectived Repeat implementations handle the -C E…… scenario in which packet#3 is lost. Mark tide any changes in the sliding windows upon communication, 10 packets receipt of messages/ACKs at either end. For Fig. 1: A typical message flow diagram for your convenience, a typical message flovw diagram for the Selective Repeat method a Selective Repeat implementation of TCP (and, ofcourse, for a different scenario) is given in Fig. I. isgiven in Fg.L (½ + ½ + 1+1-3 Mar (% + ½ + +1 _ 3 Marks) (b) In a "Selective Repear" implementation two bits are allocated for the sequence number so that the packets can be numbered 0 through 3. Explain by any problem that could arise if a sliding window size of 3 is chosen in the implementation means of a diagram, if necessary,

Explanation / Answer

The data can get lost, reordered or duplicated due to the presence of routers and buffer space over the unreliable channel in the conventional networks. The data link layer deals with frame formation, flow control, error control, and addressing and link management. All such functions will be performed only by data link protocols. The sliding window protocol will detect and correct error if the received data have enough redundant bits or repeat a retransmission of data.

Difference

GO BACK AND ARQ

SELECTIVE REPEAT ARQ

Go Back N ARQ is inefficient for noisy link.

Selective repeat ARQ is efficient for noisy links

Go Back N ARQ is less complicated than Selective repeat ARQ.

Selective Repeat ARQ is complicated

Go Back N ARQ Sender Window Size is 2^ (m)-1 and receiver window size is 1.

.in Sender and receiver Window Size is 2^ (m-1)

Go-Back-N ARQ is a specific instance of the automatic repeat request (ARQ) protocol, in which the sending process continues to send a number of frames specified by a window size even without receiving an acknowledgement (ACK) packet from the receiver. It is a special case of the general sliding window protocol with the transmit window size of N and receive window size of 1.

Selective Repeat ARQ / Selective Reject ARQ is a specific instance of the Automatic Repeat-Request (ARQ) protocol used for communications. It may be used as a protocol for the delivery and acknowledgement of message units, or it may be used as a protocol for the delivery of subdivided message sub-units.